Graduation of Arend van Roon: Detecting Flow Regime And Optimising Transport Efficiency

Arend van Roon defending his graduation thesis
Arend van Roon defending his graduation thesis

Our first happy event this year is the graduation of Arend van Roon. He recently graduated on a project in the slurry test circuit at our Research and Development department at Damen Dredging Equipment1. His research was an interesting investigation in the detection of flow regimes. It gives some insight in the processes involved in the transport of water-solids mixtures. Let me share some details from the background with you, as I think this might be helpful for your own operation also.

Overview of the Damen Dredging Equipment slurry pumping test circuit
Overview of the Damen Dredging Equipment slurry pumping test circuit

At first sight, it is hard to imagine, how something heavier than water, the grains, can be lifted when the fluid is moving. Sape Miedema has written the standard on mixture transport in his book ‘Slurry Transport’, explaining his approach with the ‘Delft Head Loss & Limit Deposit Velocity Framework2’. Without going into the academic details, I will try to help you grasp the gist of the phenomena.

DHLLDV book (Credit: Sape Miedema)
Slurry Transport text book cover (Credit: Sape Miedema)

First the grains have to be picked up. When they are lying on the bottom of the pipe, they are fully immersed, surrounded by the fluid on all sides. The free fluid on top and the pore water between the grains under and on the side of the grains. Now comes Bernoulli’s trick. When the fluid in the pipe starts moving, he says that the local dynamic pressure decreases, while the static fluid in the pores remains at the same pressure. The pressure difference between the pressure in the pores and in the moving fluid, pushes the grains out of the bed into the fluid.

Grain pickup and suspension process explained
Grain pickup and suspension process explained

Once the particles are in the fluid are in the fluid, they should stay suspended, or they fall back into the bed. The driving force here is the turbulence in the fluid. Usually dredging slurry mixtures are turbulent. This turbulence causes the fluid to flow in eddies. These are little vortices that generally move in the direction of the flow, but in a moving frame of reference tumble in all directions. Mmh, as they rotate in all directions, why don’t they cancel each other out? Now, imagine being a particle yourself, surfing on those eddies. When it is in a fluid, it tends to sink with a certain settling velocity. Independent of the local movement of the fluid. This means, that on the downward side of the eddy, the particle has a higher total velocity than on the upward side. As the eddy is sort of symmetric, the particle dwells longer in the upward draft than on the downward fall. In this infinitesimal time difference, the eddy transfers some extra kinetic energy from the fluid to the potential energy of the particle. As this loss of kinetic energy is compensated by an increase in pressure (remember Bernoulli) carrying grains in a fluid increases the pressure loss in the slurry transport.

Flow regimes and excess hydraulic gradient requirements in dredging slurry transport (Credit: Sape Miedema)
Flow regimes and excess hydraulic gradient requirements in dredging slurry transport (Credit: Sape Miedema)

This turbulence is in short the background of suspension in the slurry transport process. Depending on al the various governing parameters: densities, viscosity, diameters, velocities etc, the equilibrium of forces result in several different regimes in the slurry flow. Ranging from homogeneous, through stratified to ultimately a static bed. Each with their own particular pressure losses. And that is what we are interested in. On our dredges, we want to transport as much material to the least amount of energy3. We are constantly looking for improvements in our equipment and sensors to assist the operator in visualising and controlling the actual state of his process4. Thanks to Arend’s project and the promising results, we can set the next step in our product development.

Explanation on slurry flow conditions, critical speed and specific power consumption
Explanation on slurry flow conditions, critical speed and specific power consumption

References

  1. Innovation, Damen
  2. Slurry Transport: Fundamentals, A Historical Overview & The Delft Head Loss & Limit Deposit Velocity Framework 2nd Edition, TU Delft
  3. Innovations In The New MAD Series To Increase Uptime And Reduce Fuel Consumption, Discover Dredging
  4. Dredging Instrumentation, Damen

See also

2021: Muddling Along To A Healthy Year In Dredging

Calendar picture of a sunny dredging site
Calendar picture of a sunny dredging site

Dear readers, I sincerely wish you all the best for this new year. As things are looking positive on the vaccine front, we should keep testing negative this year. There are lots of items and events to look forward. Last year was not quite what we’ve hoped for and wished each other.

I do hope all of you are OK and are still together with your loved ones. I am fortunately in that respect. So, next to the Covid situation, there were a lot of other noteworthy items. Most of them have been featured here on Discover Dredging. My trip to Bangladesh, just before all the lockdown measures. The graduation of Carsten1 and Omar2 that were completely over Teams. Some attention to our Damen Dredging Experience3. And some other items. Did you enjoy the Donald Duck review?4

Opening scene of ‘Muddy Fine Business’ or ‘Success Test’ (Credit: Disney)
Opening scene of ‘Muddy Fine Business’ or ‘Success Test’ (Credit: Disney)

One sad event was, the last issue of Dredging and Port Construction5. We’ve had to say goodbye to our trusted DPC. Although by now, there has been a kind of digital revival on the CEDA Website6. They opened up a section for Industry News, edited by Namrata Nadkarni. It stands out from the other online media covering dredging as there has been some attention to smaller topics, that would normally not get covered. As I think it is a good initiative, I urge you to subscribe and also participate by sending them any noteworthy news items for publication. Not specifically the usual company press releases, but also the more thought provocative opinions and perspectives on the activities of our dredging community. Active participation could make this CEDA Industry News flourish this year.

Announcement of the CEDA Industry News section (Credit:CEDA)
Announcement of the CEDA Industry News section (Credit:CEDA)

Further personal activities within CEDA are the Dredging Management Commission7 and I am looking forward to the exciting new concept for the CEDA Dredging Days8. Will you participate? Also, I already took the course on ‘Dredging for Sustainable Infrastructure’9, but you should keep an eye out on the next instalment, coming soon10.

A continuation from last year on my Discover Dredging will be some more articles on our Damen Dredging Experience. There are still some exhibit left to review and teaser:… There are some new exhibits arriving! Hope to have that covered when the pandemic will fizzle out we can show you around through our museum. And I hope to continue on pump and dredge technology.

Overview of the Damen Dredging Experience
Overview of the Damen Dredging Experience

Currently, there are some students working on their graduation thesis. Their very interesting topics will be highlighted here as well. Some others will start soon. When you are looking for a fun place to have your internship our your graduation, you might consider a visit to our career page11 or contacting Frank Bosman for any opportunities. Although most positions are filled at the moment, later this year we would welcome fresh brains again.

As our offices will be closed for regular work, I will be working from home most of the time. Probably most of you will do likewise. To keep track of the passage of time over the days, you should have a calendar. As a special service to my audience, I was granted the use of a set of beautiful pictures to create a calendar. You can download the file here and with some DIY skills you should have some original wall decoration for this year.

Stay healthy and stay safe. Hope to see you later this year.

Selection of calendar pictures
Selection of calendar pictures

References

  1. Graduation Of Carsten Markus: Designing And Casting Of Impellers, Discover Dredging
  2. Graduation Omar Karam: Rock Cutting The Egyptian Way, Discover Dredging
  3. Selected articles on the Damen Dredging Experience, Discover Dredging
  4. Book Review: Donald Duck A Muddy Fine Business; Artistic Equipment Design; Discover Dredging
  5. The Last Dredging And Port Construction Magazine, The End Of An Era; Discover Dredging
  6. Debut of CEDA Industry News section and monthly newsletter, CEDA
  7. Selected articles on the CEDA Dredging Management Commission, Discover Dredging
  8. Call for Papers for CEDA Dredging Days 2021 issued, CEDA
  9. Book Review: Dredging For Sustainable Infrastructure, Discover Dredging
  10. 2nd Online Course Dredging for Sustainable Infrastructure planned for March 2021!, IADC
  11. Welcome to the best years of your life, Damen

See also

Book Review: Dredging For Sustainable Infrastructure

‘Dredging for Sustainable Infrastructure’ (Credit: CEDA & IADC)
‘Dredging for Sustainable Infrastructure’ (Credit: CEDA & IADC)

Last week, I attended the last sessions of the ‘Dredging for Sustainable Infrastructure’ course, jointly organised by CEDA1 and IADC2. This course is intended to quickly absorb the contents of the book of the same name3 and have a hands on experience of the novel methodology proposed. The book has been written by many different people as members of the participating organisations. As such, it is the condensed knowledge and ideas of the dredging community on a modern approach to infrastructure projects. Although there is a straightforward structure in the book, the publishers initiated courses as an introduction to the book.

Structure of the book (Credit: CEDA & IADC)
Structure of the book (Credit: CEDA & IADC)

As Covid-19 swept across Europe and thwarted the intended live course days, the sessions were postponed and eventually held online. The presenters, Erik van Eekelen, Thomas Vijverberg and Mark Lee did a good job of introducing us to the book and supervise us in the break out working groups. The central storyline of the working groups was the harbour expansion of the fictional port of Tomigo in the fairy land of Quandany. Each of the participants was assigned a role to represent the consultant, the fishing community, the nature conservancy organisations, the power plant etc. A revelation for me from this interaction is how easy you are inclined to be egocentric in the defence of your interests. With just a little more attention to the other interests, there might be much better opportunities for yourself and for the whole of the project.

New harbour basin development at the port of Tomigo (Credit: CEDA & IADC)
New harbour basin development at the port of Tomigo (Credit: CEDA & IADC)

The incentive to produce a book on this novel approach in dredging projects was the UN initiative to launch 17 Sustainable Development Goals4 and the book addresses most of these goals. If we can truly lift the proposed working procedures into an industry standard or even a social mentality, this will be a paradigm shift from where the project was the centre of attention to: ‘Where can nature and society benefit from an economic requirement?’ The next step will be from philosophy to action.

United Nations ‘Sustainable Development Goals (Credit: United Nations)
United Nations ‘Sustainable Development Goals (Credit: United Nations)

The focus of the book is very much on the initial stages of a project: include sustainability on the basis of the design of a project, demonstrating options for sustainable solutions suggestion of sustainable techniques. As a dredging equipment manufacturer5, most of the topics will not affect my daily work. Still, in the work group sessions, it was interesting to see the interaction between the various parties that are involved with the initiation of a project. As a dredge builder4, we usually meet the requirements for the equipment applied. Though, the technical solution to achieve this might be not the most commercial solution. However, the book makes it clear and provides examples, that taking all aspects of a project into account, including social and nature opportunities, the benefits of a sustainable approach of a project might still make a viable business case.

Three pillars of sustainability (Credit: CEDA & IADC)
Three pillars of sustainability (Credit: CEDA & IADC)

The verdict on the book: it is a reference book. And as such it is very tiresome to plough through. However, the course is very enlightening as introductory lectures into the contents. Then the meticulously compiled information starts to live. Don’t depend on the courses alone, also leaf through and note all the valuable tables, graphs and diagrams, especially the guiding boxes that can assist you in setting up your dredging project. It definitely belongs on your bookshelf.

‘Dredging for Sustainable Infrastructure’ in our bookshelf
‘Dredging for Sustainable Infrastructure’ in our bookshelf

References

  1. CEDA and IADC launches new ‘Dredging for Sustainable Infrastructure’ Course, CEDA
  2. Online Course ‘Dredging for Sustainable Infrastructure’, IADC
  3. Dredging for Sustainable Infrastructure, CEDA&IADC
  4. The 17 goals, United Nations
  5. Damen Dredging Equipment, Damen

See also